Not answering query

About R3500 bill received for data usage. Tried through about 6 online and branch queries. I want an invoice for that month but I did not get it. Through all queries I got a reply from only one saying that invoice is on its way but did not get it. I will cancel all contracts when end date is due and will tell everybody of Mtn's bad service. I was a very long time client. I already cancelled this number but still have 2 contracts left. I refused to pay until investigated but was threatened by service suspension.